[AnalyticalPhill]

Hi all,

I work in an analytical testing lab. I've recently been asked to identify the active (API) in a pharmaceutical tablet and all I see is polyvinylpyrrolidone, a seemingly intractable polymer that appears to be used more and more in modern pharmaceuticals. I've tried aqueous extractions, but the stuff just will not go away. Does anyone know of a quick, accessible and cost effective method to remove PVP and isolate sufficient active for an ID?

Many thanks,
Phill

[marquis]

How are you trying to ID the active?  IR, chromatography, or some other method?

[AnalyticalPhill]

Thanks for the reply.

IR is our main method because we have a good set of reference libraries. Mass spec is a usual second option, but the active appears more recent than our most recent MS reference library. The IR of the tablet and of the extracts is just PVP.

[marquis]

This is a crude method that has worked for additives on other polymers.  I haven't done much work on PVP, so I don't know the solvents to use.  It only works on polymers that are not crosslinked.  Maybe it will help get you started.

You need two solvents.  The first solvent should dissolve both you active and the PVP.  The second solvent should dissolve the active.  The two solvents should be miscible.

Dissolve your material into a minimum amount of the first solvent.  Add a relatively large amount of the second solvent.  The PVP, since it isn't soluble, should precipitate out.  Filter the mixture and evaporate the solvents to get your active.

The polymer example-  You take a small amount of compounded polyvinyl chloride (PVC) and dissolve it in 5 ml tetrahydrofuran (THF).  Add 15 ml methanol and mix well.  The PVC precipitates out.  Filter, evaporate, and run IR on the residue to id the additives.

There maybe other materials in the product that will mess this up, but it is a starting point.  Good luck.

[AnalyticalPhill]

Thanks for the reply. I will certainly give it a go. Unfortunately, from my experience so far, PVP seems to be soluble in everything. It's a water soluble polymer originally used in harisprays of the sixties and has now found a use in pharmaceutical tablets. It's also very soluble in chloroform and it formed an emulsion the last time I tried extracting it. Thinking about your answer though, the key may be to try and and solubilise everything and precipitate out the active by acid/base treatment to adjust protonation state and thereby the water / solvent solubility that way. I will give this a try and see how it goes. Thanks for the inspiration. Other than this, I'm still looking for alternative methods if anyone has any plans I can try.